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Antivenin (Micrurus fulvius)

Generic name: antivenin (micrurus fulvius) systemic

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution Reconstituted, Intravenous:

Generic: (1 ea)


Mechanism of Action

Antibodies neutralize the venom components, thereby blocking the effects of the Eastern coral snake (Micrurus fulvius) and Texas coral snake (Micrurus tener) venom

Use: Labeled Indications

Micrurus fulvius fulvius (Eastern coral snake) or M. f. tener (Texas coral snake) envenomation: Treatment of envenomation by an Eastern coral snake (M. f. fulvius) or Texas coral snake (M. f. tener). The antivenin may not be effective in the management of other Micrurus species (Ramos 2016).


There are no contraindications in patients with life- or limb-threatening envenomation.

The concomitant administration of opioid analgesics or other analgesics that depress respiration is contraindicated.

Note: Clinicians should be prepared to manage severe, immediate hypersensitivity reactions especially in patients known be allergic to antivenin (Micrurus fulvius) or horse serum (either by history of or as a result of an appropriate sensitivity test).

Dosage and Administration

Dosing: Adult

Sensitivity testing: Intradermal skin test should be performed prior to antivenin administration:

Skin test: Intradermal: 0.02 to 0.03 mL of a 1:10 dilution of normal horse serum or antivenin; evaluate against a control test (intradermal injection of NS on the opposite extremity). A 1:100 or greater dilution should be used if the patient’s history suggests hypersensitivity. Note: A positive reaction is an urticarial wheal with or without pseudopodia surrounded by a zone of erythema appearing within 5 to 30 minutes.

Desensitization: Note: In separate vials or syringes, prepare 1:10 and 1:100 dilutions of antivenin in NS.

SubQ: Inject 0.1 mL, 0.2 mL, and 0.5 mL of the 1:100 dilution at 15-minute intervals. During this procedure, proceed with the next dose only if a reaction has NOT occurred following the previous dose. Repeat the procedure using the 1:10 dilution and then undiluted antivenin. If no reaction has occurred following administration of 0.5 mL of undiluted antivenin, switch to IM administration and continue doubling the dose at 15-minute intervals until the entire dose has been administered or administer the usual IV dose.

If a reaction occurs, apply a tourniquet proximal to the injection site and administer epinephrine (1 mg/mL) proximal to the tourniquet or into another extremity. Wait at least 30 minutes; then administer another antivenin injection at the previous dilution which did not evoke a reaction.

Micrurus fulvius (Eastern coral snake) or M. tener (Texas coral snake) envenomation: IV: 30 to 50 mL (3 to 5 vials) by slow injection (dependent on severity of signs/symptoms; some patients may need more than 10 vials).

Note: Each vial of antivenom neutralizes ~2 mg of venom.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Sensitivity testing: Refer to adult dosing.

Desensitization: Refer to adult dosing.

Micrurus fulvius (Eastern coral snake) or M. tener (Texas coral snake) envenomation: Children and Adolescents: IV: Refer to adult dosing.


Dilute each vial with SWFI 10 mL. Vial contains a vacuum which will pull the diluent in; point diluent stream at the center of the lyophilized pellet. If diluent runs down side of vial, the pellet will float and adhere to vial stopper, thereby rendering complete reconstitution difficult. Swirl gently for 1 minute; do not shake. Repeat every 5 minutes. Reconstitution takes ~30 minutes/vial. The color of the final solution may vary from clear to slight yellow or green.


IV: Have ready access to medications and equipment for resuscitation. An IV infusion of NS 250 to 500 mL should be started, and the doses of antivenin should be delivered by slow injection or via reservoir bottle. Inject the first 1 to 2 mL of antivenin over 3 to 5 minutes with careful observation for the development of a hypersensitivity reaction. The rate of infusion for the remaining antivenin will be regulated by tolerance to the antivenin and the severity of envenomation.


Prior to reconstitution, store at 2°C to 8°C (36°F to 46°F). Do not freeze.

Note: As of February 2019, FDA announced the expiration dating of antivenin lot number L67530 has been extended through January 31, 2020.

Drug Interactions

There are no known significant interactions.

Adverse Reactions

Frequency not defined.

Immediate reactions:

Immediate reactions may occur within 30 minutes and may start before needle is withdrawn. Symptoms include apprehension, collapse, cough, cyanosis, dyspnea, facial edema, flushing, laryngeal edema, pruritus, tongue edema, urticaria, vomiting.

Cardiovascular: Shock

Hypersensitivity: Anaphylaxis, hypersensitivity reaction

Delayed reactions:

Delayed reactions occur 5 to 24 days following administration. Symptoms include arthralgia, edema, fever, lymphadenopathy, malaise, nausea, urticaria, vomiting. Neurological symptoms (eg, amyotrophy, meningism, myasthenia, pain, and peripheral neuritis) may also occur.

Hypersensitivity: Serum sickness


Concerns related to adverse effects:

  • Delayed serum sickness: Delayed serum sickness may occur 1 to 3 weeks from administration (especially when large doses used) even with a negative allergic history and absence of reaction to skin test.
  • Horse serum hypersensitivity: Carefully review allergies and history of exposure to products containing horse serum. History of atopic sensitivity to horses may increase risk of immediate sensitivity reactions. Use with caution in patients with asthma, hay fever, or urticaria.

Concurrent drug therapy issues:

  • Beta-blockers: Concomitant use with beta-blockers may prolong and increase the severity of acute anaphylaxis.
  • Sedatives/opioids: Use sedatives with extreme caution; concomitant use with opioids or other analgesics that suppress respiration is contraindicated.

Other warnings/precautions:

  • Appropriate use: North American coral snake envenomation: Do not administer prophylactically to asymptomatic patients. Clinicians should note that antivenin (Micrurus fulvius) does not neutralize venom of the Arizona or Sonoran coral snake (Micruroides euryoxanthus).
  • Desensitization: A desensitization protocol is available if sensitivity tests are mildly or questionably positive to reduce risk of immediate severe hypersensitivity reaction. According to the manufacturer, desensitization should be performed when antivenin administration would be lifesaving; however, the risk of anaphylaxis should be weighed against the risks associated with delayed antivenin administration.
  • Resuscitation precautions: All patients require close monitoring in a setting that has ready access to medications and equipment for resuscitation.
  • Skin test: The manufacturer recommends that a skin test be performed prior to administration; however, the utility of skin tests to accurately identify patients at risk of early (anaphylactic) or late (serum sickness) hypersensitivity reactions to horse-derived antivenins has been questioned (Klaewsongkram 2009; WHO 2005). The absence of a skin hypersensitivity reaction does not exclude anaphylaxis or hypersensitivity following antivenin administration. False-negative rate for skin testing is 10% with similar agents. Conversely, hypersensitivity is not an absolute contraindication in a significantly envenomated patient.

Monitoring Parameters

Resolution of symptoms of envenomation or emergence of symptoms of hypersensitivity to the antivenin; respiratory function and oxygenation; urine for hemoglobinuria


Pregnancy Considerations

In general, medications used as antidotes should take into consideration the health and prognosis of the mother.

Patient Education

What is this drug used for?

  • It is used to treat North American coral snake bites.

Frequently reported side effects of this drug:

  • Vomiting
  • Abdominal pain

Other side effects of this drug: Talk with your doctor right away if you have any of these signs of:

  • Loss of strength and energy
  • Cough
  • Shortness of breath
  • Severe dizziness
  • Passing out
  • Fast heartbeat
  • Swollen gland
  • Joint pain
  • Muscle pain
  • Signs of a significant reaction like wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from the healthcare provider. You must talk with the healthcare provider for complete information about the risks and benefits of using this medicine.

Source: Wolters Kluwer Health. Last updated November 22, 2019.